Fusible plug flame detection system



Sept. 20, 1966 F. FULLER, JR

FUSIBLE PLUG FLAME DETECTION SYSTEM 2 Sheets-Sheet 1 Filed Feb. 25, 1964FIGZ w wrw w \J Q a INVENTOR.

FULLER, JR.

FIG

FORNEY A TTORNE Y Sept. 20, 1966 F. FULLER, JR 3,274,579

FUSIBLE PLUG FLAME DETECTION SYSTEM Filed Feb. 25, 1964 2 Sheets-Sheet 2FIG] A ION 30 I l h FIGI B FIG. 3 A 500) INVENTOR.

FQRNEY FULLER JR BY W ATTORNEY 3,274,579 FUSIBLE PLUG FLAME DETECTIONSYSTEM Forney Fuller, Jr., P.0. Box 12151, New Orleans, La. Filed Feb.25, 1964, Ser. No. 347,157 6 Claims. (Cl. 340-227) This inventionrelates to furnaces and fuel burners associated therewith. Moreparticularly, the invention relates to the detection of heat associatedwith the burners when burning fuels such as natural gas, oil, pulverizedcoal, cellulose Waste, waste combustibleliquids, as in black liquorrecovery furnaces, and any combination of fuels burned simultaneously inthe same furnace.

On any type of fuel fired furnace, one instance being the commonhousehold gas cooking range, it is important to detect the absence of aflame While gas is still being supplied to the burner. In privatedwellings employing gas cooking ranges, the absence of a flame while gasis still being supplied is generally quite rapidly observed by the odorof the issuing gas and hence preexplosive conditions due to theaccumulation of large quantities of flammable gas in a room or otherinstallation are avoided.

In distinction to the ease with which the housewife notices the lack ofa flame While gas is being supplied to a burner, industrialinstallations require a more positive method for detecting the absenceof a flame. In industrial installations, the accumulation of largequantities of combustible gases attendant a flameout is not onlydangerous to life but the large capital investments make it mandatorythat a satisfactory flameout detection system be available.

Prior workers in this art have taught flame failure indicator systems,such as Atwater, U.S. Patent 2,396,146 and Thomson, U.S. Patent2,692,962, to mention only two of a variety of such systems. The effortsof prior workers in this field have generally been satisfactory and thepresent invention will provide workers in this area with yet anotherflame failure apparatus.

It is now recognized by workers in this field that fuel fired furnacesare inherently safe if the furnace space (or envelope) is held above thekindling temperature of the fuel or fuels being fired. With mostcommercial fuels this is thought to be 1500 F. Heretofore most flamefailure detection has been by detection of light emitted from the flame.Conditions of burning can change and frequently this changes the wavelength of light emitted, thereby making limited Wave length detectorsinoperable.

According to the present invention, the heat from ignited fuel burnersis employed to melt fusible plugs in an endless tape. The melting of thefusible plugs is a positive indication that the gas burners are flaming.The failure of the fusible plugs in the endless belt to melt is apositive indication that there has been a flame failure within thefurnace or the furnace temperature has dropped below the safe kindlingtemperature. Suitable means are employed to detect either the melting ornon-melting of the fusible plugs, such detection being suitably coupledto the fuel supply so as to cut off the latter when there is no flame orinstitute other safety measures such as purging the furnace withnitrogen or steam.

Accordingly, it is an object of the present invention to provide a flamefailure indicating system for a furnace or other installation employingfuel burners.

It is a further object of the present invention to provide a flamefailure indication system employing a movable probe travelling past theburners of a burner installation wherein the probe includes a pluralityof 3,274,579 Patented Sept. 20, 1966 fusible elements whose melting orfailure to melt indicates the presence or absence of the flames in theburners.

It is a further object of the present invention to provide a flamefailure indication system for a furnace or other installation employinga fuel burner wherein a movable and endless belt passes through theinterior of an installation employing a fuel burner and wherein theendless belt contains a plurality of fusible elements and the melting orfailure to melt of the fusible elements is an indication of the presenceor absence of a flame.

These and other objects will become apparent from the followingdescription.

In the drawings:

FIG. 1 is a partially schematic view of the flame failure indicationsystem of the present invention, being a cross-section of a largefurnace having burners therein in combination with an endless flamedetection belt.

FIGS. 1A and 1B are similar to FIG. 1 and show variations in thelocation of the endless belt.

FIG. 2 is a partially schematic and perspective view of a portion of theendless belt of the present invention in combination with an opticalmeans for detecting the melting or non-melting of a plurality of fusibleplugs in the belt.

FIG. 3 is a partially schematic view showing the flame failureindication system of the present invention employed to detect flamefailure in a plurality of banks of gas burners.

FIG. 3A is similar to FIG. 3 and shows only a single burner.

The FIGURES 1, 1A, 1B show the invention as it may be used to detectfurnace temperature at a relatively remote point from the burners, toassure that furnace safety is being maintained when the furnacetemperature is above the minimum kindling temperature of the fuel beingfired.

Referring now to FIG. 1 of the drawings, the numeral 10 denotesgenerally a cross-sectional view taken of a large furnace. Thecommercial embodiments of large furnaces exhibit wide variations indesign and the reader is requested to note that the illustrated furnaceis but one of a large number with which the present flame failureindication system according to the present invention may be employed.The numeral 12 denotes an endless belt or tape formed of metal ofsuitable flexibility and high melting point. The endless belt issupported by four pulleys denoted by the numeral 14 and motion in theindicated direction is afforded by a motor 16 coupled either directly toone of the pulleys 14 by raised Wheel face engaging the tape holes, orindirectly, as by friction, to the movable belt 12. The numerals 18 and20 denote apertures leading, respectively, into and out of the furnacefor the passage of the belt therein and thereout. Sealing of apertures18 and 20 is effected by blocks 19 and 21, see FIG. 2. The numeral 22denotes a cooling device which may, in one form, consist of a cool airblast, cool oil bath, or water spray for cooling the endless tape afterpassing through the combustion zone of the furnace 10. A fusible pluginserter denoted by the numeral 24 is positioned adjacent a lower run ofthe belt 12 and in association therewith a conventional photocell system26 is positioned. The photocell arrangement 26 inspects the belt andinsures that the mechanism 24 is operating properly, i.e., that afusible plug is inserted in each of the holes of the tape 12.

The numerals 30 and 32 denote elements of a detection system which, inone form, consist of a photocell and a light source such as Laser, Maseror incandescent.

A Laser beam can be made of different degrees on intensity. It should bejust intense enough to penetrate dust atmosphere or smoke that may bepresent in the furnace; but not intense enough to damage its receiver orother parts that may come in contact with the beam. For ease ofillustration, the elements 30 and 32 are shown as positioned exteriorlyof the furnace 10. In practice it will be observed that the elements 30and 32 may also be placed either within the furnacelt) or the furnacewalls are provided with high temperature glass or other transparentsubstances. The numeral 34 denotes an alarm suitably coupled withdetection elements 30 and 32. In practice, the alarm 34 is linked withthe fuel input to the burners of the furnace so that a flame failure (tobe described in detail later) results in the cessation of fuel fed tothe furnace.

The numeral 50 denotes burners within furnace 10, and the numeral 52denotes a combustion zone adjacent these burners. It will be observedthat the tape 12 passes, in the indicated direction of travel,substantially medially of the combustion zone 52.

Referring now to FIGURE 2 of the drawings, the numerals 36 denoteapertures in the endless belt 12, the latter here being shown in threedistinct sections for purposes of illustrations. The numerals 38 denotefusible plugs within apertures 36, these being the fusible plugs whichmechanism 24 inserts. The numeral 40 denotes the fusible plugs 38 atvarious stages of melting as the belt 12 passes upwardly within furnace1t) and into the combustion zone 52. The fusible plug material whenmelted is removed by a combination of vaporization and by solid removalthrough the ash discharge system always located at the bottom of afurnace.

A description of the above-described elements will now be set forth,illustrating a preferred mode of operation of the flame failureindication system according to the present invention. Assuming thefurnace to be in full operation with the burners 50 ignited and flamewithin the combustion zone 52 performing the intended heating functionwithin the furnace 10, a portion of the endless belt 12 to the right ofphotocell system in FIG. 1 passes into the furnace 10 through aperture18 and thence begins its upward travel. As it nears the combustion zone52, the heat due to the flames causes the fusible plugs 38 to melt, thisprogressive melting being indicated at 40 at FIG. 2. It will be observedthat the lower run of tape 12 in FIG. 2 contains plugs completely intactwhile the upper run of the tape 12 shows the plugs as having beencompletely melted. Thus, with continued upward movement of the tape 12,the fusible plugs 38 become completely melted after having passedthrough combustion zone 52 and when they reach the area of the plugdetection elements 30 and 32, the plugs 38 have all melted and the lightfrom the detection system passes through the apertures 36 indicatingthat the furnace burners are operating as intended. After having passedthrough the combustion zone 52 and the interior of the furnace 10, thetape 12 is quite hot and for this purpose the cooling device 22 isemployed to lower the temperature. This portion of the tape now passesaround to the plug insertion mechanism 24 where new plugs 38 areinserted in the holes and the operation of the system is as abovedescribed. I

In the event of a flame failure within the furnace 10, and a resultantlowering of furnace temperature the plugs do not melt or, if they domelt, they will melt incompletely so that the light from detectionelements 30, 32 does not pass through apertures 36 thus giving anindication, by means of the alarm 34, that there has been a flamefailure. In such an instance, by suitable circuitry so well known byworkers in this art as not to require description thereof at this point,the input to the fuel burners 50 is cut off, thus precluding the escapeof flammable fuel vapor which otherwise would create a potentiallydangerous explosive situation in the installation.

Referring now to FIG. 3 'of the drawings, the practice of the presentinvention on a furnace employing a single burner or a plurality of banksof burners is illustrated.

FIGURES 3 and 3A show the invention used adjacent to a burner or groupof burners where the flame may actually impinge against the tape andfusible plugs. In

this case a higher melting temperature plug is used and detection offlame out on one burner or group of burners can be detected. In FIGURES3 and 3A with the ex ception of the fusible plug detection elements, thenumerals correspond to those of FIGURES 1 and 2 with a zero added. Thus,the numeral 120 in FIGURE 3 corresponds to the element 12 of FIGURES 1and 2. Referring to the detection arrangement of the embodiment ofFIGURE 3, with a plurality of tapes 120 for the purpose of detecting aflame failure in any one of a plurality of burner banks 590 in furnace100, the numeral denotes a source of light (also Maser and Laser source)while numerals 62, 64 and 66 denote light-sensitive elements such asphotocells which are mounted, respectively, on pivoted elements 68, 70and 72. In operation, where it is desired to detect the presence orabsence of fusible plugs in the upper belt 120, gate 68 is placed in theillustrated position and light source 60 cooperates with photocellelement 62 to make the determination. Assuming that the upper burnerbank 500 is operating properly, the flames therefrom will have meltedall of the plugs in the upper belt 120 and now gate 68 which carriesphotocell 62 is swung clockwise and the beam from source 60 may now beused to detect the presence or absence of fusible plugs in the middlebelt 120. Thus, in the arrangement illustrated in FIGURE 3, one lightsource 60 may be employed to test a plurality of belts 120.

It will be observed that in the embodiment of FIG- URE 1, the fusibleplug detection elements 30 and 32 are placed quite near the combustionzone 52, thus necessitating the use of high temperature resistantelements 30 and 32 or the use of transparent materials in the walls ofthe furnace 10. This is in distinction to the arrangement of FIGURE 3wherein the fusible plug detection mechanism is located eXteriorly ofthe furnace. Either arrangement may be employed, and it will be observedthat the greater cost necessitated by the arrangement of FIGURE 1 yieldsthe desired result of detecting the absence of a melted plug morerapidly. In FIGURES 1A and 1B, the detection tape passes horizontallythrough the furnace, through the kindling temperature zone thereof. Thisarrangement may be employed when the width of a furnace 12 permits thetape to traverse the furnace in sufficient time to assure safe detectionexteriorly of the furnace. This permits the use of conventionalphotocelldetection elements 30 and 32 in lieu of Laser and Maser.

What is claimed is:

1. A flame failure detection system including a static installationhaving a fuel burner therein, a probe provided with a plurality oflongitudinally spaced apertures adapted to contain fusible elements,said probe positioned at least partially within said static installationand adjacent said fuel burner, and means to detect the condition of thesaid fusible elements, whereby detection of melting of the fusibleelements indicates an ignition condition of the fuel burner anddetection of the fusible elements as not melting indicates anon-ignition condition.

2. A flame failure indication system comprising a static installationhaving a fuel burner mounted therein, an endless belt having at leastone portion therein passing through said static installation andadjacent said burner, said belt having a plurality of apertures therein,means for placing a fusible plug within each of said apertures, andmeans for detecting the melting of said fusible plugs to therebydetermine the presence of a flame in the fuel burner.

3. The system of claim 2 wherein said detection means includes a sourceof radiation adapted to shine against a portion of said endless belt.

4. The flame detection system of claim 2 including means to insertfusible plugs in said tape and means for moving said belt into and outof said static installation.

5. The flame failure indication system of claim 2 including alarm meanscoupled to said fusible plug melting detection means, said alarm meansbeing coupled to the fuel input to said burner to thereby cut off saidfuel input when a fusible plug has not melted.

5 6 6. The method of detecting flame failure in a static ReferencesCited by the Examiner installation having a tuel burner thereinincluding the UNITED STATES PATENTS steps of contlnuously msertmg andWithdrawing from a combustion area within said static installation aprobe 1,953,072 4/1934 Casper 340339 X having a plurality of spacedfusible elements thereon, 5 335L876 9/1962 Brown 34O 2'27 detecting themelting or non-melting of fusible elements and continuously providingsaid probe with new fusible NEIL READ lmary Exammer' elements. R. M.ANGUS, Assistant Examiner.

6. THE METHOD OF DETECTING FLAME FAILURE IN A STATIC INSTALLATION HAVINGA FUEL BURNER THEREIN INCLUDING THE STEPS OF CONTINUOUSLY INSERTING ANDWITHDRAWING FROM A COMBUSTION AREA WITHIN SAID STATIC INSTALLATION APROBE HAVING A PLURALITY OF SPACED FUSIBLE ELEMENTS THEREON, DETECTINGTHE MELTING OR NON-MELTING OF FUSIBLE ELEMENTS AND CONTINUOUSLYPROVIDING SAID PROBE WITH NEW FUSIBLE ELEMENTS.